1. Field of the Invention
The present invention relates to a surge arrester, and more particularly to a surge arrester including two current-conducting connection fittings separated by an axially symmetrical active portion of the surge arrester.
2. Brief Description of the Related Art
EP 0 614 198 B1 describes a surge arrester containing two connection fittings and a column of varistor elements, stacked one above the other, between the connection fittings. Electrical contact between the connection fittings and the varistor elements is produced by two or more loops of insulating material, the ends of which are respectively mounted in one of the two connection fittings, and thus also act with a contact force on the varistor elements located therebetween.
For large constructional heights, as are for example required for nominal voltages of more than 70 kV, a surge arrester constructed according to EP 0 614 198 B1 is generally not used, as relatively expensive additional measures have to be provided in its manufacture.
A surge arrester is described in EP 0 335 479 B1 which includes a weather protection housing, two connection fittings brought out of the housing, and an active portion of axially symmetrical construction, located in the interior of the housing, arranged between the connection fittings. The active portion is constructed from several cylindrical modules, which are stacked one above the other in the form of a column. Each module has several cylindrical varistor elements whose ends abut along the cylinder axis. Electrical contact between the varistor elements is attained by the substantially axially-directed thread winding which acts with a pre-stressing force on two metallic end portions which bind the module at the ends. The end portions of adjacent modules are electrically connected together by means of a screw bolt.
The production of a surge arrester as described in EP 0 335 479 B1 is relatively expensive, since the modules are produced by thread winding in a first step, and in a succeeding second step the modules are then joined together by screwing adjacent end portions of the modules, with the formation of a connecting portion having good electrical conductivity.